Because of the complex demands for trunk piston lubricating oil compositions in lubricating all regions of trunk piston engines, much effort has been made to develop lubricating oil compositions that perform well with conventional high sulfur heavy fuel oils.
With increasing health and environmental concerns regarding the use of high sulfur heavy fuel oils, however, there is an increasing likelihood that low sulfur marine residual fuel use in trunk piston engines will become the norm, or even mandated.
While conventional lubricating oil compositions used, to this point, in trunk piston engines operating on conventional heavy fuel oils and diesel fuels might function to some degree with low sulfur marine residual fuels, they likely are ill-suited for such usage and would not ensure optimum performance, such as in neutralizing acid combustion gases, maintaining engine cleanliness, and resisting viscosity increase.
Some attempts have been made, therefore, to produce a lubricating oil composition for use with fuels with specified sulfur content. For example, EP 1486556 is directed to a method for lubricating crosshead marine diesel engines that operates on a fuel having a sulfur content of less than 1.5%, using a cylinder lubricant composition that comprises a detergent complex. Moreover, EP 1790710 is directed to a method for operating a marine engine by lubricating the engine with a single cylinder lubricant that comprises an overbased metal detergent. Moreover, WO/2006064138 is directed to a method for operating a marine four-stroke engine operating on fuels of varying sulfur content, which comprises lubricating the engine with a lubricating oil composition that contains a detergent.
A need still remains, however, for improved lubricating oil composition for use in low sulfur marine residual fuels that achieve optimum performance.